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Old 06-23-2010, 04:11 AM   #1
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Join Date: May 2006
Location: Los Angeles
Posts: 125
My Ride: 2000 323i
P1188, P1189, etc Codes Fixed Easily (1 Oil Separator Hose) (*Pics*)

For some time, I have had these codes with the SES light on:

Usually, but not always, with one or more of these codes:
P1250 (especially this one)
P0170 (P0171 on M54 & M56 engines)
P0173 (P0174 on M54 & M56 engines)

Freeze frame data on my scanner recorded lean conditions at idle, such as:
STFT B1: 18.75%
LTFT B1: 8.59%
STFT B2: 17.97%
LTFT B2: 8.59%

Bottom line: it was the easily accessible, and commonly broken, lower oil separator vent hose. Here is the story...

Only symptom was a slightly rough idle just after start-up, but idle okay when warm (people in colder climates may have more severe symptoms, however). Usually these codes denote a problem with a vacuum leak, probably either due to a crack(s) in the large rubber air intake boots between the MAF sensor and the engine block or due to a problem with the oil separator (also known as the pressure regulating valve, crankcase ventilation valve [CCV, CVV], PCV valve, cyclone separator [some spell it "seperator"], etc) or its 4 associated vent hoses. In my case, the intake boots were okay (checked during a very recent intake control valve (ICV) cleaning). I did not have any "chewbacca/walrus" noises coming from the engine when the oil filler cap was removed at idle, which would be evidence of a bad oil separator itself. Since many people find a broken lower oil separator hose (the one that goes to the oil dipstick tube) during their oil separator replacements, I decided to check this hose first.

I found that it was indeed broken just below the oil separator in the usual spot. Replacement of this one hose fixed all my codes and service engine light (it's been ~2 weeks now), and finally allowed me to get my smog inspection! The BMW part number is 11157532649, which I think is correct for all E46 models except the 316, 318 and M3 (but check it on or parts company websites for your particular car). The hose with pinch clip connector is only about $10 from your favorite online parts company. The hose is part #4 in picture #4 (oil separator is part #1; picture from, although the shape of the hose is not curved as shown, but rather is straight with a plastic angled elbow at the oil separator end.

I strongly suggest that people who are thinking of replacing their oil separator (a big job) to check this hose first -- it could save (or at least postpone a few years) you a LOT of time and trouble. It's an easy and fast replacement. This hose can be checked visually and replaced after removing only the air filter box and MAF, if you know where to look (a light helps). The attached pictures should help you locate it. This hose has one of those pinch-clip connectors at the connection to the oil separator, so just squeeze it to disconnect (check your new hose if you're not familiar with these). The lower part just has a friction connection to the oil dipstick tube (some silicone lube will help you connect this end). No need to remove the dipstick tube. You can also view and work with the hose/dipstick connection from beneath with the splash pan removed.

When I replaced mine, I had first removed the braid-covered hose (the large one in all of these pictures) from the steering fluid reservoir, because it was causing a steering fluid leak (separate issue). This gave me more room to work, but I think you can push things (wires, tubes) out of the way as you work your hand in there without removing this steering fluid hose. If not, you can always unbolt the steering fluid reservoir and tilt it and its hose out of the way (after removing some reservoir fluid with a turkey baster if necessary).

For reference, my car is 10 years old but only has ~60,000 mi.

Pic #1: General area of lower oil separator hose location.

Pic #2: Closeup showing break in hose.

Pic #3: A closer closeup showing break in hose.

Attached Pic #4: diagram of oil separator system.
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Last edited by gsbmw; 07-09-2010 at 05:14 PM.
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